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Abstract

Plant responses to environmental stimuli are co-ordinated by a variety of sensing and signalling mechanisms, which bring appropriate internal changes so that plants are able
to adapt to a changing environment. It was the aim of this project to investigate the regulation of one gene: DARK INDUCIBLE 3 (DIN3), specifically the cis- and transacting
factors. To achieve these aims, the investigative approach centred on gene expression analysis of linker-scan mutation analysis of 50 base-pairs (bp) of the minimal functional promoter of DIN3. To investigate the contribution made by transacting factors, the effects of over-expression of candidate transcription factor genes were analysed. This project determined that in addition to dark-induced expression already described in the literature, the dark-induction of DIN3 expression could be repressed by low temperature. Specific motifs within the crucial 50bp of the DIN3 promoter were found to be necessary for dark-induced expression, which together was hypothesised to constitute a sugar-responsive sequence. No cis-acting regulatory motifs
were found to contribute definitely to the cold responsiveness of DIN3. None of the transcription factor genes investigated, were revealed to have a major role in the dark and cold responsiveness of DIN3. The results of this project suggest that there is considerable cross-talk between dark/sugar regulation and low temperature at the cisand trans-acting level.